JIS-B 6339 - MAS 403 BT Toolholders. Suitable for a wide range of applications from rough milling to finishing and for use with cylindrical milling cutters, drill bits and precision tools. Centering is guaranteed by the surface of the cone. All Pagnoni Toolholders are 100% tested with certified measuring instruments. Balancing performed where indicated. Any additional balancing is performed on customer request up to a maximum class of G2.5 at 30000 rpm.